236 Scientific Intelligence. 
thin layers of limestone and gypsum. But the — between this 
formation and the Triassic is stated to ts uncertai 
The Medicine Bow Range is made up seve exclusively of 
rchean crystalline rocks, inclu ding granites, | mica 
athints: hornblende schists, diorytes, argillytes, quartzytes, ete. 
e granite and gneiss contain much of a triclinic feldspar, and 
in some places zircons. At Cherokee Butte, there is a 
granite whose quartz grains 
of wear, and hence of the metamorphic origin of the rock. Medi- 
contains some cyanite. It is cut through by what appears to be 
dikes of a fine-grained dioryte. The Archean quartzyte is under- 
by a hornblendic rect At Mill Peak, the quartzyte is and 
overlaid by a red conglomerate, and, above the conglomerate, 
gem bebet Lee ealeareou us. 
The Nort and Park Range are described at length by 
Mr. pes only a few facts os eal the voleanic rocks are 
lifted by the erupted trachytes. East of Parkview Peak the 
eruptive rock of some of the hills is granitoid and porphyritic, 
though probably related to the trachytes, Zirkel calls the rock 
granite-porphyry. The eruptions are not older than Cretaceous. 
The basalt of the divide between the two Parks lies almost en- 
tirely westward of the trachytic region 
The Elkhead Mountains are described by Mr. Emmons. They 
are a group of high volcanic peaks, some over 10,000 feet above 
the sea-level. They include the north-and-south elevations of 
some places, chryeolite, as desctibved by Zirkel. There 
seems to have been a transition from the e trachytic outflows In 
Hantz Peak to eons In the basalt of Bastion Peak occur, be- 
sides the ordinary constituents and nephelite, some chrysolite, ‘and 
plateau increases westward from 4,300 to 6, 000 feet, Ruby Valley, 
sete the east base of the Humboldt range, being the highest por- 
tion. The valleys are mostly under Quaternary fiepoutte coarse 
5 
PEARS, WR ine as ae SENSE 
